Optica Squares
I love geometrical patterns and optical illusions, so this was a natural to make, from a piece by Simon C Page, which I first saw at Peano's Tumblr. To dynamicize it, I thought about being able to change the rate of shrinking, which is still linear, and the amount of turning, in addition to the number in a row.
Original: http://blog.excites.co.uk/post/127390598771/optica-prints-some-available with several more neat variations.
More GeoGebra at bit.ly/mh-ggb